The fire fighters were working their way through the top floor of the building unit by unit.

Once this was completed, crews would begin damping down hot spots, assistant area commander Paul Smith said. He expected this would be completed tomorrow morning.

The ground floor appeared to have escaped with only water and smoke damage.

"The fire is deep-seated and we expect to be still fighting the fire tomorrow morning. Once it has been extinguished then a fire investigation will begin to determine the cause,'' Mr Smith said.

"Our advice is for commercial property owners of large buildings to install sprinklers _ that way any fire that does start is either doused by the sprinklers or stopped from spreading until firefighters arrive.''

Earlier this afternoon a digger was used to pull off part of the roof and a side wall, removing some of the energy from the fire and allowing firefighters to direct foam inside.

A cinematographer who worked on Sir Peter Jackson's Lord of the Rings trilogy, Alex Funke, feared a couple of Oscar awards had been lost in the blaze.

"Where that smoke right there is,'' he said, pointing to the unit most damaged.

The awards were for the Two Towers and Return of the King.

Mr Funke believed the Academy would be able to replace the awards. ``But it's not quite the same thing, is it?''

He said there were also some Bafta awards in the unit.

"But more important is all my camera equipment that was in there.''

He did not realise until today that the units didn't have sprinklers.

Mr Funke didn't know how much the items were worth, but they had "a great deal of personal value".

"It's very upsetting. You put stuff in a storeroom and you say `Well, it's safe, nobody's going to steal it, it's never going to burn down'. Well obviously next time put it in a place with sprinklers.''

Alex Funke. Photo / APNZ

Andrew Fraser, director of the parent company which owns Kiwi Self Storage said sprinklers were not installed at the storage unit because it was not industry practice to do so.

Smoke detectors, which were connected to an alarm system, alerted people to the blaze.

"We have also on-site managers that live at the facility. They were obviously aware of the alarm and immediately contacted the fire department.''

Photo / SNPA / Ross Setford

It was not yet known what caused the fire, which has caused extensive damage to one of the five Kiwi Self Storage units at the Kilbirnie facility.

"Fortunately the fire department have succeeded in containing the fire to the one building. Unfortunately it's the largest of the buildings,'' Mr Fraser said.

The company would likely be discussing the use of sprinklers in its units, he said.

Flights at Wellington Airport, close to the storage facility, had not been affected.